This application claims the priority of Application No. 101 41 721.7, filed Aug. 25, 2001, in Germany, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a supporting arm of a passenger door of an aircraft, comprising a curved structure which forms hollow chambers and movably connects the passenger door to a frame on the fuselage, there being formed on the supporting arm receiving means for receiving connecting means which enable a movable connection on the one hand to the passenger door and a pivoting drive and on the other hand to the frame on the fuselage, so that the door is movable by means of the supporting arm on a linear-displacement path and a pivoting path.
The passenger door opens and closes the fuselage opening to the passenger compartment (passenger cabin) of an aircraft.
The passenger door (also referred to as door hereinbelow) of an aircraft is mounted and held movably on a supporting arm by means of two triangular links. The supporting arm is arranged rotatably on the aircraft frame on the fuselage. Furthermore, an emergency opening drive, e.g. cylinder with push rod, is fastened on the one hand to the supporting arm and on the other hand to the door. This emergency opening drive allows the door to be moved in an emergency.
In the case of aircraft which are in service, this supporting arm is cast or milled in one piece from an aluminum alloy. This metal supporting arm produced in one piece has a hollow chamber design and is structurally optimized with regard to its aluminum alloy and its material thicknesses. The supporting arm constitutes a curved body which, in top plan view, has an outline curved in an L-shaped manner.
To receive connecting means, there are formed on the supporting arm receiving means, which are formed at the end faces of the supporting arm.
With respect to the frame on the fuselage, the supporting arm is mounted with its end-face receiving means on an axis of rotation arranged on the frame.
At the other end face of the supporting arm, receiving means there carry the triangular links, which are connected movably to the door.
The emergency opening drive is likewise held and mounted in a receiving means of the supporting arm, a force transmission means of the emergency opening drive being connected to the door.
The movement of the door is generally associated with the movement of the supporting arm.
The supporting arm guides the door during the opening and closing operation on a linear-displacement path and a pivoting path. In the process, the supporting arm carries the entire weight of the door and takes up stresses.
In the opened state of the door, the supporting arm inevitably reduces the emergency opening cross-section of the door opening. Its external shape, found hitherto, forms an optimum between the narrowing of the emergency opening cross-section and its functional tasks. There is therefore no desire to alter the external shape of the supporting arm.
This supporting arm forms a joint which movably connects the passenger door to the frame on the fuselage. For this purpose, there are formed on the supporting arm receiving means which enable a movable connection on the one hand to the passenger door and an emergency opening drive and on the other hand to the frame on the fuselage.
During an opening and closing operation, this supporting arm thus performs a joint function and movement function and, in an emergency, a so-called emergency opening function.
The supporting arm has to cope with complicated force flows (longitudinal and transverse forces, bending and torsional forces) in a confined space volume. For this reason, only materials with an isotropic structure have been employed for the supporting arm hitherto.
From the large number of possible stresses on a supporting arm, two serious stresses emerge. One of these stresses arises in the event of a fault involving a possible blockage of the door as it is being lifted and the other stress arises during the spreading-out as a result of the force of the emergency opening drive during the pivoting movement of the door.
The supporting arm, produced with a hollow chamber design, withstands these great stresses; nevertheless, in aircraft construction an improved lightweight construction of the door and hence a reduced weight of the supporting arm are also called for. Despite producing the supporting arm from cast aluminum, this supporting arm is still of relatively high weight.
Furthermore, the low thermal insulation of the supporting arm at cruising altitude is disadvantageous. After only one hour of flying, at an internal temperature of the cabin of 23xc2x0 C. the supporting arm has a surface temperature of only about 8.5xc2x0 C. This low temperature influences the well-being of the passenger sitting in the immediate vicinity.
An object of the invention is to further improve the thermal insulation of a supporting arm and nevertheless achieve a further weight reduction of the supporting arm, while maintaining exacting structural safety requirements for the latter.
The invention relates to a supporting arm of a passenger door of an aircraft. This supporting arm comprises a body which is curved in a substantially L-shaped manner and in which hollow chambers are formed. The L-shaped body runs in a substantially elongated and relatively flat manner, and then bends approximately at right angles in an end region. Its outer contour corresponds to the known contour of a supporting arm made of aluminum. According to the invention, the structure of the supporting arm is formed from fiber composite, an anisotropic material.
Fiber composite consists of fiber material which is embedded in a matrix of cured reaction resin compound. The supporting arm may, for example, consist of carbon fiber composite (CFC).
The structure-forming fiber composite is formed from individual structural elements. These structural elements are formed by fiber textile elements which are impregnated and cured in a production process.
The supporting arm made of fiber composite is produced in an RTM (Resin Transfer Molding) process. The RTM process uses in principle a mould, the mould comprising an upper mould part and a lower mould part, into which a preform is placeable in a precise-fitting manner.
The supporting arm made of fiber composite is produced by means of such an RTM process. In the production using an RTM process, the supporting arm is built up from individual fiber textile elements into a preform, i.e. assembled.
Fiber textile elements comprise a fiber arrangement which is already held by a matrix preimpregnated to a small extent. As a result of the RTM process, fiber textile elements form the structure of the supporting arm.
In order to build up such a preform for the RTM process, individual fiber textile elements are arranged in a manner appropriate to the stresses. The preform forms a semi-finished fiber textile product assembled into a single piece.
As the individual fiber textile elements for the preform, use is made of at least:
belt elements made of woven fabric as longitudinally running webs for taking up preferably longitudinal forces,
thick laminates as outer edge elements (wall elements) for taking up transverse forces and the bearing stress,
belt covering elements,
wherein a belt element lying in a horizontal plane is vertically spaced from a belt element lying in a different horizontal plane, and in a projection of the belt elements onto a horizontal plane, the belt elements are arranged, lying in the contour between top belt and bottom belt, so as to form a belt skeleton, and the belt elements are spaced and connected, in the region of the end faces of the belt elements, by belt covering elements, and the belt skeleton is connected by means of the narrow sides of the belt elements on both sides to an outer skin element in each case.
Alternatively, the individual fiber textile elements can also be arranged in such a way that a belt element lying in a horizontal plane runs with one end into a different horizontal plane and another belt element lying there runs with its end back into the plane of the belt element, so that both belt elements cross, and the belt elements are bounded, vertically spaced, by a top belt element and a bottom belt element, and the belt elements are spaced and connected, in the region of the end faces of the belt elements, by belt covering elements, and the belt skeleton is connected by means of the narrow sides of the belt elements on both sides to an outer skin element in each case.
At least the three fiber textile elements mentioned form a belt skeleton which forms hollow chambers.
The belt element has as the fiber textile element a multidirectional fiber orientation. This is particularly advantageous with regard to the stresses.
The individual fiber textile elements are joined together, for example, by sewing, bonding or the like, so as to produce a three-dimensional body, the preform, which forms a plurality of hollow chambers. The preform corresponds to the external shape and the structure of the supporting arm. This preform is placed into the mould for an RTM process. The upper mould part and the lower mould part, as well as possible inserts (mould cores), enclose the preform and result in a closed and sealed mould. For shaping reasons, individual mould cores may be necessary in the mould. However, this is not a requirement. Formed on the mould are attachment means. Each attachment means is connected to a resin injection device and a suction device. Both devices are controllable.
The heated and thus liquid reaction resin compound is injected under pressure into the closed mould. In the process, suction is applied at an opposite point on the mould. After complete impregnation, the preform is cured.
The reaction resin compound is a mixture of resin, hardener and additives and is referred to for short as xe2x80x9cresinxe2x80x9d hereinbelow. After the curing, the upper mould part and lower mould part are separated and the produced component is a supporting arm made of fiber composite. The supporting arm is then cleaned. Bores are made as attachment means for the connecting means. Metal bushes are bonded into the bores.
The supporting arm can also be produced, alternatively, with a half-shell design using a prepreg process.
The invention is explained below with the aid of individual exemplary embodiments and associated drawings.